Searching for a Cosmological Preferred Axis: Union2 Data Analysis and Comparison with Other Probes

Abstract

We review, compare and extend recent studies searching for evidence for a preferred cosmological axis. We start from the Union2 SnIa dataset and use the hemisphere comparison method to search for a preferred axis in the data. We find that the hemisphere of maximum accelerating expansion rate is in the direction $(l,b)=({309^{\circ }}_{-3^{\circ }}^{+23^{\circ }},{18^{\circ }}_{-10^{\circ }}^{+11^{\circ }})$ ($\omm=0.19$) while the hemisphere of minimum acceleration is in the opposite direction $(l,b)=({129^{\circ }}_{-3^{\circ }}^{+23^{\circ }},{-18^{\circ }}_{-11^{\circ }}^{+10^{\circ }})$ ($\omm=0.30$). The level of anisotropy is described by the normalized difference of the best fit values of $\omm$ between the two hemispheres in the context of \lcdm fits. We find a maximum anisotropy level in the Union2 data of $\frac{Δ\ommax}{\bomm}=0.43\pm 0.06$. Such a level does not necessarily correspond to statistically significant anisotropy because it is reproduced by about $30$ of simulated isotropic data mimicking the best fit Union2 dataset. However, when combined with the axes directions of other cosmological observations (bulk velocity flow axis, three axes of CMB low multipole moments and quasar optical polarization alignment axis), the statistical evidence for a cosmological anisotropy increases dramatically. We estimate the probability that the above independent six axes directions would be so close in the sky to be less than $1$. Thus either the relative coincidence of these six axes is a very large statistical fluctuation or there is an underlying physical or systematic reason that leads to their correlation.

10 pages, 7 figures. Accepted in JCAP (to appear). Extended analysis with redshift tomography of SnIa, included errorbars and increased number of axes. The Mathematica 7 files with the data used for the production of the figures along with a Powerpoint file with additional figures may be downloaded from http://leandros.physics.uoi.gr/anisotropy

References in corpus (26)

• Improved Cosmological Constraints from New, Old and Combined Supernova Datasets
• Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
• Improved Dark Energy Constraints from ~100 New CfA Supernova Type Ia Light Curves
• The Uncorrelated Universe: Statistical Anisotropy and the Vanishing Angular Correlation Function in WMAP Years 1-3
• Instability of anisotropic cosmological solutions supported by vector fields
• Confronting Lemaitre-Tolman-Bondi models with Observational Cosmology
• Testing LCDM with the Growth Function δ(a): Current Constraints
• Optimal limits on f_{NL}^{local} from WMAP 5-year data
• Cosmic Microwave Background Statistics for a Direction-Dependent Primordial Power Spectrum
• Instability of the ACW model, and problems with massive vectors during inflation
• Combining Lens Distortion and Depletion to Map the Mass Distribution of A1689
• Anisotropic Cosmological Constant and the CMB Quadrupole Anomaly
• Testing the Void against Cosmological data: fitting CMB, BAO, SN and H0
• Local Void vs Dark Energy: Confrontation with WMAP and Type Ia Supernovae
• A Model of Universe Anisotropization
• CMB Temperature Anisotropy from Broken Spatial Isotropy due to an Homogeneous Cosmological Magnetic Field
• Cosmological perturbations from vector inflation
• Direction-Dependent CMB Power Spectrum and Statistical Anisotropy from Noncommutative Geometry
• On the Possibility of Anisotropic Curvature in Cosmology
• Creating Statistically Anisotropic and Inhomogeneous Perturbations
• Six Puzzles for LCDM Cosmology
• Constraining dark energy fluctuations with supernova correlations
• Giant Rings in the CMB Sky
• The Shape and Topology of the Universe
• Evidence for a Preferred Handedness of Spiral Galaxies
• Non-gaussianity and Statistical Anisotropy in Cosmological Inflationary Models

Cited by in corpus (105)

• Challenges for $\Lambda$CDM: An update
• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Is the Observable Universe Consistent with the Cosmological Principle?
• Probing the anisotropic local universe and beyond with SNe Ia data
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• Probing the isotropy of cosmic acceleration traced by Type Ia supernovae
• Is there Correlation between Fine Structure and Dark Energy Cosmic Dipoles?
• Testing the Isotropy of the Universe with Type Ia Supernovae
• Constraints on anisotropic cosmic expansion from supernovae
• Exact solution of vacuum field equation in Finsler spacetime
• Hints of a Local Matter Underdensity or Modified Gravity in the Low $z$ Pantheon data
• Complexity and Isotropization based Extended Models in the context of Electromagnetic Field: An Implication of Minimal Gravitational Decoupling
• Constraining the Anisotropic Expansion of Universe
• Direction Dependence of the Deceleration Parameter
• Hubble flow variance and the cosmic rest frame
• Observational constraints on the deceleration parameter in a tilted universe
• Probing the anisotropic expansion from supernovae and GRBs in a model-independent way
• Probing Cosmological Isotropy With Type IA Supernovae
• Testing the isotropy of the Universe by using the JLA compilation of type-Ia supernovae
• CMB Maximum Temperature Asymmetry Axis: Alignment with Other Cosmic Asymmetries
• Searching for a preferred direction with Union2.1 data
• Peculiar motions, accelerated expansion and the cosmological axis
• Anisotropy of the Universe via the Pantheon supernovae sample revisited
• Null Signal for the Cosmic Anisotropy in the Pantheon Supernovae Data
• Cosmological Solutions through Gravitational Decoupling in $f(\mathcal{R},\mathcal{T},{\mathcal{R}}_{\mathrm{ab}}{\mathcal{T}}^{\mathrm{ab}})$ Gravity
• Anisotropy of Cosmic Acceleration
• Inference of the cosmic rest-frame from supernovae Ia
• Cosmological model with local symmetry of very special relativity and constraints on it from supernovae
• The significance of anisotropic signals hiding in the type Ia supernovae
• Probing bulk flow with nearby SNe Ia data
• Light propagation in a homogeneous and anisotropic universe
• Testing the isotropy of the Universe with type Ia supernovae in a model-independent way
• Anisotropic cosmological reconstruction in $f(R,T)$ gravity
• Global and Local Effects of Rotation: Observational Aspects
• Geodesic-light-cone coordinates and the Bianchi I spacetime
• Directional dependence of CMB parity asymmetry
• Bianchi I meets the Hubble diagram
• Internal Robustness: systematic search for systematic bias in SN Ia data
• Isotropy of low redshift type Ia Supernovae: A Bayesian analysis
• Anisotropy of the galaxy cluster X-ray luminosity-temperature relation
• Constraining the anisotropy of the Universe via Pantheon supernovae sample
• Anisotropic expansion and SNIa: an open issue
• Percent-Level Test of Isotropic Expansion Using Type Ia Supernovae
• Constraining anisotropy of the universe from different groups of type-Ia supernovae
• The deceleration parameter in `tilted' Friedmann universes
• Testing the anisotropy of cosmic acceleration from Pantheon supernovae sample
• Dynamical analysis of cosmological models with non-Abelian gauge vector fields
• Inflation and primordial power spectra at anisotropic spacetime inspired by Planck's constraints on isotropy of CMB
• Generalized LTB model with Inhomogeneous Isotropic Dark Energy: Observational Constraints
• Testing cosmic anisotropy with Pantheon sample and quasars at high redshifts
• Probing cosmological isotropy with Planck Sunyaev-Zeldovich galaxy clusters
• Light propagation in inhomogeneous and anisotropic cosmologies
• Bianchi Type I model of universe with customized scale factors
• Weak-lensing by the large scale structure in a spatially anisotropic universe: theory and predictions
• Is there evidence for anomalous dipole anisotropy in the large-scale structure?
• Testing the Cosmic Anisotropy with Supernovae Data: Hemisphere Comparison and Dipole Fitting
• A Model-independent Test of Cosmic Isotropy with Low-z Pantheon Supernovae
• The multipole expansion of the local expansion rate
• Constraining the Anisotropy of the Universe from Supernovae and Gamma-ray Bursts
• Cosmological Constant, Fine Structure Constant and Beyond
• Dynamical features of an anisotropic cosmological model
• Constraining the local variance of $H_0$ from directional analyses
• The peculiar Raychaudhuri equation
• Ultra-compact radio sources and the isotropy and homogeneity of the Universe
• The deceleration parameter in `tilted' universes: generalising the Friedmann background
• Searching for a cosmological preferred direction with 147 rotationally supported galaxies
• Searching for a Cosmological Preferred Axis in complicated class of cosmological models:Case study $f(R,T)$ model
• A tomographic test of cosmological principle using the JLA compilation of type Ia supernovae
• Accelerating anisotropic cosmologies in Brans-Dicke gravity coupled to a mass-varying vector field
• Testing cosmic anisotropy with Pade approximation and Pantheon+ sample
• Non-comoving Cosmology
• Probing the isotropy of cosmic acceleration using different supernova samples
• Testing the isotropy of cosmic acceleration with Pantheon+ and SH0ES: A cosmographic analysis
• Two fluid anisotropic dark energy models in a scale invariant theory
• Cosmography of the Local Universe by Multipole Analysis of the Expansion Rate Fluctuation Field
• Extending Finch-Skea Isotropic Model to Anisotropic Domain in Modified $f(\mathcal{R},\mathcal{T})$ Gravity
• Consistency of Pantheon+ supernovae with a large-scale isotropic universe
• Supernovae anisotropy power spectrum
• Topological Quintessence
• Anisotropic universe with anisotropic dark energy
• On Topological Modifications of Newton's Law
• Searching for Cosmological Preferred Axis using cosmographic approach
• Implications of Rastall Theory on Stellar Solutions admitting Vanishing Complexity: A New Perspective
• Testing the anisotropy of the universe using the simulated gravitational wave events from advanced LIGO and Virgo
• SNe Ia Tests of Quintessence Tracker Cosmology in an Anisotropic Background
• Testing Local Anisotropy Using the Method of Smoothed Residuals I - Methodology
• Probing the anisotropic distribution of baryon matter in the Universe using fast radio bursts
• High-z Supernova Type Ia Data: non-Gaussianity and Direction Dependence
• Falsifying Cosmological Constant
• Testing the anisotropy of the Universe with the distance duality relation
• Cornering the axion-like particle explanation of quasar polarisations
• Constraints on Bianchi-I type universe with SH0ES anchored Pantheon+ SNIa data
• Expanding covariant cosmography of the local Universe: incorporating the snap and axial symmetry
• Analysis of recent type Ia supernova data based on evolving dark energy models
• Spinning Toroidal Brane Cosmology; A Classical and Quantum Survey
• Distance-Redshift Relations in an Anisotropic Cosmological Model
• New Constraints on Anisotropic Expansion from Supernovae Type Ia
• The prospects of gravitational waves on constraining the anisotropy of the Universe
• Can Chameleon fields be the source of both the dark energy dipole and the CMB dipole?
• Constraining Axially Symmetric Bianchi Type I Model with Self-Consistent Recombination History and Observables
• Large Scale Cosmological Anomalies and Inhomogeneous Dark Energy
• Expansion of a spherical dust gas -- the cosmological conundrum
• Testing the cosmological principle on gigaparsec scales
• Constraints on the dark energy dipole from large-scale structures
• Dark Energy Induced Anisotropy in Cosmic Expansion